Metal inclosed electrical apparatus



Feb. 2, 1932. H. J. HUBER METAL INCLOSED ELECTRICAL APPARATUS Filed Nov. 29, 1930 Fig.

Inventor: Harm an J. Hubm".

Fig.2.

LJLZX H is Atfiorn 0 Patented Feb. 2, 1932 2 t; STATES.

PATENT OFFICE,

HERMAN .1. HUBER; or UPPER n-ARBY, PENNSYiiVANIA, Assrenon 'ro GENERAL DIELECTRIC coMPANx CORPORATION OF NEW YORK I ME'r L mctosnn ELECTRICAL APPARATUS E Application filed November 29, 1930.- SeriaLNo. 493,036. 3

Man invention relates to metal inclosed electcicfih apparatus and more particularly to means for: bracing, electrical conductors in metal clad switchgear against large short circuitistresses-as at connections requiring flex ibleconnections, between a. cable vand an" insulatin zbushing of brittle material.

In: us;and .switch stations of the so-called metal cladztype wherein the individual phase connections; are, encased 0r armored by a grounded;metallicisheathing, the short circuitrstresses, particularly in high. voltage stations, ofi-large capacity, may. be of suchmagnitudethatvthe:conductors or cables within l6-"the -metal; sheathing are given a: powerful longitudinal thrustior .lrick? tending to damage the, connections atv the brittle porcelain insulating bushings leading from the cable.

connections'to the circuit breakers and other apparatusin the station; In these large stations theconductors .o'r c'ables are generally ofrsuch large sizeand great. weight that it 1 is notppracticalitoconnect them directly to v porcelainshells or insulatorsinside the metal a heavy short circuit: Heretofore, the metal inolo'sed' conductors have been supported andimounted, by spacing collars and similar deviceszd'epending mainlyon the friction between the: same and. the; inclosing. casing for preventing movement; of the conductor.

v While-:such: an arrangement may be satisfactony for lower capacity stations, due to the fact-athatxthe short-circuitstresses in this case are notof.suchzmagnitude :as to cause appreciable: movement; of the spacing collars, the/same is ineffective for high capacity stationsisuc'has 2J/ millions kit-a. capacity for instances: 3: i .1

'} the event thattthe heavy: conductor is not; adequately. braced 011heldnxin; its proper position, ".chatt ering may resu'ltdue to the vibration perinjttediby the insecure bracing.

This is considered by operating. companies to be an objectional-featuresinceon heavy currents the chattering may becontinuous. F urthermore, av heavy short circuit may tear the flexible connection from the top of? the shell' or break the porcelain unless the conductor at the otherend of the flexibleconnection is firmly secured in position.

A further consideration with respectto the, bracing structure for the heavy-conductor is that of creepagedistance; that; is, the'distanee along the insulating parts between the live conducting portions andv the grounded metal casing. In order to have alarge factor of safety, this creepage distance should: be a maximum for the design involved. It follows, therefore, that the most advantageous design combines maximum creepage distanceewith maximum bracing effect on the co'nductons A principal object of my invention isthe provision of improved'means forbracing a metal encased heavy conductor, with respectto large short circuitstresses which shall be simple in construction and in application.

A" further object of myinvention is the provision of improved bracing structure for metal clad conductors which is eflective positively to brace the conductor with respect to. either tension or compression short circuitstresses and which involves a maximum creepage distance.

hilyinvention will be more fully set forth in the following description referring to the accompanying drawings, andthe features of. novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part ofthis; specification.

Referring to the drawings, Fig.- l'is a fragmentary elevational view, part-1y insection, alongthe line 1-l of Fig. 20f metal clad switchgear embodying; my. invention, and Fig; 2. is across sectional-plan view taken alonggthe line-2.2 of Fig.

The portion of metal clad switchgear shown in Fig.1 comprises ametallicii'nclosing casingl, as a casting,suitablyconnected to ametall-icpipe or sheathing2 inclosing the heavy insulated conductor or cable-13:; In;

general practice, the metallic inclosing structure is filled with oil or other suitable insulating material and the connections are sealed as by a suitable gasket 4 so as to'be fluid tight. Thelower part of the casing 1 may be connected through the hollow insulator shell 5 constructed of porcelain or the like, to electrical apparatus as circuit breakers or disconnecting switches in a manner well known in the metal clad art. A cylindrical insulating shield 6 may be interposed between the insulator shell and the metallic casing 1.

For the purpose of flexibly connecting the heavy cable 3 to the :conducting portion 7 mounted on and extending through the insulator shell, flexible-braid conductors-8 are used, thesame being bolted or otherwise suitably secured to the interconnected parts as better shown in Fig. 2. Accordingly, a lim- 1 ited amount of movement of the proeelain shell with respect to the cable, asby conconductor 3 and the walls of the inclosing casing so that the abutting surfaces are substantially in the direction of thrust of-said conductor.

The bracing structure'in' the present'in-j stance comprises an A-frame having two legs 9 and 10 suitably connected at one endas by the bolts-11 and braced by the-cross member 12 to complete the A-frame. The diverging ends of the legs 9 and 10 are beveled to abut firmly the inner side of the casting 1 as shown, and the connected ends abut the Wall or web 1 of the casting so that the structure is rigidly positioned with respect to the casting. The connection between the conductor 3and the bracing structure comprises a pair of rigid metallic strips 13 and 14 which are bolted as at 15 to the end 3' of the conductor 3 :and to mid-portions of the legs 9 and 10 as at 16 and 17 respectively. Accordingly, the conductor is positively braced against longitudinal movement in either direction, tension on the strips 13 and 14; tending to Wedge the legs 9 and 10 'into firmer engagement with the casting and compression on the strips forcing theconvergingportion of the A- frame against the wall 1'. Since the cross member 12 prevents relative movement of the legs '9 and 10 and therefore prevents any lateral movement of the A-frame within the stresses. r

The upper part of the casting 1 is provided with a cover plate 18 for sealing the casting after assembly or inspection. The bracing structure may be assembled and secured in posit-ion within the casting 1 without difficulty through the opening in the casting since the A-frame may be readily bolted or secured together within the casting and thereafter connected by the strips 13, and 14 to the conductor 3. a

It will be noted that the creepage distance from the ends of the metal strips 13 and 14 which are connected at 16 and 17 respectively to the bracing structure is practically a maximum for the particular design involved. That is, the connection to each of the legs 9 andlO is substantially at mid-portions sothat the distance to the nearest portion of the grounded casing issubstantially the same in all cases and is suflicient to prevent flash-"- over under most severe operating conditions.

It shall be understood that my invention is not limited to specific details 'of construction and arrangement thereof herein-illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent in the United States is: a

1. In metal inclosed electrical apparatus. including metallic inclosing structure and an electrical conductor mounted therein, means.

for bracing and holding said electrical conductor with respect to longitudinal movement thereof comprising an insulating frame rigidly-mounted within said structure, and means for securing said-conductor to said frame so that longitudinal thrusts of said conductor in either direction are transmitted directly by said frame to said structure.

- 2. In metal inclosed electrical apparatus including a metallic inclosing structure and an electrical conductor mounted therein,

means for bracing and holdingsaid electricalconductor with respect to longitudinal movement comprisin an insulating frame dis posed substantia ly in the same plane as the longitudinal axis of said conductor, said frame being rigidly mounted within and abutting the walls of said structure, and means for securing said conductor to said frame so that longitudinal thrusts of said conductor in either direction are transmitted directly by said frame to said structure.

3. In metal inclosed electrical apparatus including a grounded metallic casing and an electrical conductor mounted therein, means for bracing said electrical conductor against large short circuit stresses tending to cause longitudinal movement of said conductor comprising an insulating A-frame abutting and rigidly mounted within said casing, the

abutting surfaces of said frame being sub+-s stantially in the direction of the trust of said conductor, and means for rigidly securing said conductor to an intermediate portion of said A-frame so that longitudinal movement of said conductor in either direction is prevented.

4. Metal clad electrical apparatus comprising a grounded metallic casing, a comparatively massive electrical conductor spaced from and mounted within said casing, anwinsulating shell of comparatively brittle material mounted within said casing, a conducting portion mounted on said insulating shell, said conductor and conducting portion being 4 electrically connected by flexible conductors for precluding transmission of shock from said conductor to said insulating shell, and means for bracing and holding said conductor with respect to longitudinal movement due to heavy short circuits comprising an A- frame vof insulating material abutting and rigidly mounted within said casing, the abutting surfaces of said frame arranged so as to directly oppose the thrust of said conductor, and metallic means for rigidly securing an end'of said conductor to an intermediate portion of said frame so that longitudinal movement of said conductor in either direction is prevented and a large creepage distance between'said securing means and said grounded casing is obtained.

5. Metal clad electrical apparatus comprising a grounded metallic casing, a comparatively massive electrical conductor spaced from and mounted within said casing,

a porcelain insulating shell mounted within sald casing and extending substantially at right angles to said conductor, a conducting portion mounted on said insulating shell, said conductor and conducting portion being electrically connected by flexible braided conductors for precluding transmission of shock from said conductor to said'insulating shell, and means for bracing and holding said conductor with respect to heavy short circuit thrusts comprising an A-frame of insulating material abutting and rigidly mounted within said casing, said frame being interposed between said conductor and said casing in the direction of thrust of said conductor, and rigid metallic strips for securing said conductor at said flexible connection to an intermediate portion of said frame substantially midway between the abutting surfaces of said casing so that longitudinal movement of said conductor in either direction is prevented, said frame having a large creepage distance between said metallic strips and the abutting surfaces of said grounded casing. In witness whereof, I have hereunto set my hand this 26th day of. November, 1930.

HERMAN J. HUBER. 

